Prior art and contemporary connectors of the type disclosed herein are fixed to circuit boards in a number of ways. For convenience and flexibility, it has been known to manufacture electronic circuits and their connectors in a modular design for installation onto printed circuit boards of standard dimensions. Connectors have been fixed to circuit boards in several ways. For example, leads or pins may be inserted into holes in the circuit board and either soldered therein, or retained by other means, such as frictional retention means or spring means, which prevent the pin from exiting the hole in the circuit board. Conductive pads may be incorporated into the board onto which the contacts are soldered forming either a perpendicular or a parallel mount.
In present day electronics, miniaturization has led to the installation of a large number of electronic components onto a circuit board so that a large number of functions can be performed by the circuitry on the board. Consequently, the number of terminals needed for connection to other electronic components has increased, necessitating the need for high contact density, i.e., connectors having a large number of electrical contacts or terminals per unit volume.
Such connectors have been used in many applications where a surface mounted device necessitates connection of electrical contact terminals to the circuitry on the circuit board. Such applications have included, among others, memory card connections and other devices intended to introduce external input into the circuit system, as well as internal circuitry devices, such as additional circuitry, capacitors, resistors and other electronic components. For example, in the electrical connector industry, it is well known to provide an electrical connector useful for signal transmission and reception between a memory card and the circuit of a machine concerned. For reference, the Personal Computer Memory Card International Association ("PCMCIA") established memory card (or "PC Card") standards defining the PC Card's physical outline standards, connector system and qualification test parameters, including reliability, durability and environmental test parameter. PC Card Standard, Release 2.0, PCMCIA (September 1991).
Connectors having the capability of housing a high density of electrical contacts are shown in for example, U.S Pat. No. 4,583,807 issued to Kaufman et al., wherein contacts are positioned in parallel rows along the longitudinal axis of the connector housing, with tail sections extending rearwardly and downwardly from the housing which are soldered to the board.
Contact density, however, cannot generally be increased by simply placing the contacts closer together or by forming several rows of contact elements located one above the other. Increasing density in this way may result in undesirable mutual electrical interference between the contact elements, and further, the use of very long tails on contacts will increase problems due to the occurrence of undesirable inductive couplings and susceptibility to electromagnetic noise. An example of a modular connector system which cures some of these problems is U.S Pat. No. 4,992,052 issued to Verhoevan, showing a connector module with a high contact density wherein the contacts are positioned in rows, and the end of a contact in the upper row and the end of a contact in a lower row are mutually displaced, such as by offsetting the connecting ends to extend within a side edge of a base section.
Another problem in the prior art connectors has been in determining the integrity of the soldering joint affixing the contact to the circuit board. In industry, solder joint integrity has generally been accomplished through visual inspection, with an inspection device, such as a detector beam, used to view the solder joint. As shown in FIGS. 1 and 2, this has been a problem where multiple rows of contacts 20', one above the other, are present in the connector module 10', and the connections include bent tail sections that contact the circuit board in a line extending from the housing 12'. When multiple rows of contacts 20' are present in this configuration, the contact points 38' of the lower rows of contacts with the circuit board are hidden from view by the extending electrical contacts 20' of the upper rows of contacts. In these devices, the contact solder joint most proximate to the circuit board is hidden from the line of sight extending perpendicularly from the board, making visual inspection difficult. Moreover, repair of such a solder joint is difficult.
One attempt to solve this problem is disclosed in U.S. Pat. No. 4,732,365 issued to Ito et al. which describes an electrical connector having a plurality of pins defining a connecting portion for connecting the pins to an electrical element and a terminal portion for connecting the pins to one conductor of a printed circuit board. As described in FIG. 2 of Ito et al., a pin header (20) consists of a main body (22) having a plurality of pins (24) arranged in two parallel rows at the female connector side. The pins (24) are deformed within the main body so as to project from the main body (22) with the upper row forming a straight row of the terminal portions nearer the main body (22) and the lower row pins forming a straight line of the terminal portions further from main body (22). As evident, Ito et al. requires that the pin header (20) be molded around the pins (24) in order to accommodate the deformed shape of the pins (24) in the main body (22). Another attempt to solve this problem is disclosed in U.S Pat. No. 4,756,696 issued to Whiteman, where the parallel rows of contacts are offset so that a contact extending from an upper row alternately forms a connection with the circuit board from a contact extending from the lower row, the connections all being soldered on the circuit board in a single line.
While the above described patents disclose improved techniques for mounting high density electrical connectors onto a circuit board, none provides the important advantage of a high density electrical connector wherein the integrity of the solder joint or connection between the electrical contacts and the circuit board is readily susceptible to visual inspection, an also to inspection through the use of optical detectors commonly used in industry. Moreover, none of these devices discloses a high density electrical connector with the simplified repair ability of defective solder joints. Also, none of these devises discloses high density devices which may be stacked one on top of the other.